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Environment-Friendly Agricultural Research Institute, Jeollanamdo Agricultural Research and Extension Services, Naju 520-715, Korea(Received on October 26, 2011; Revised on November 13, 2011; Accepted on November 16, 2011)Fusarium wilt caused by Fusarium oxysporum hasbecome a serious problem world-wide and relies heavilyon chemical fungicides. We selected Pseudomonas sp.NJ134 to develop an effective biocontrol strategy. Thisstrain shows strong antagonistic activity against F. oxy-sporum. Biochemical analyses of ethyl-acetate extractsof NJ134 culture filtrates showed that 2,4-diacetyl-phloroglucinol (DAPG) was the major compound inhibit-ing in vitro growth of F. oxysporum. DAPG productionwas greatly enhanced in the NJ134 strain by addingmannitol to the growth media, and in vitro antagonisticactivity against F. oxysporum increased. Bioformulationsdeveloped from growth of NJ134 in sterile bean mediawith mannitol as the carbon source under plastic bagsresulted in effective biocontrol efficacy against Fusariumwilt. The efficacy of the bioformulated product depend-ed on the carbon source and dose. Mannitol amendmentin the bean-based formulation showed strong effectivebiocontrol against tomato Fusarium wilt through increas-ed DAPG levels and a higher cell density compared tothat in a glucose-amended formulation. These resultssuggest that this bioformulated product could be a neweffective biocontrol system to control Fusarium wilt inthe field.Keywords : antibiotics, soilborne disease, bioformulation,nutrient, long term survivalFusarium wilt caused by Fusarium oxysporum is a serioussoilborne disease in tomato cultivation areas worldwide(Ishikawa et al., 2005). The rapid adoption of organicagriculture in the past decades has dramatically increasedthe demand for biopesticides that can be used to controltomato Fusarium wilt. Several antagonist microorganismswith broad-spectrum activity show promise for suppressingtomato Fusarium wilt. Biocontrol agents such as Pseudo-monas spp., the fungus Trichoderna spp., and non-patho-genic Fusarium have reduced tomato Fusarium wilt ingreenhouse experiments (Shishido et al., 2005; Yigit andDikilitas, 2007). A talc-based bioformulation of Strepto-myces sp. has been used to control Fusarium wilt in thegreenhouse (Anitha and Rabeeth, 2009).Numerous fluorescent Pseudomonas spp. have beenisolated and characterized for their ability to suppress soil-borne diseases through the production of various secondarymetabolites, such as phenazines, pyrrolnitrin, and 2,4-diacetylphloroglucinol (DAPG) (Keel et al., 1996). DAPGis a polyketide antibiotic with broad spectrum antimicrobialproperties and is produced by fluorescent Pseudomonasspp. of diverse genotypes and geographic origins (Keel etal., 1996; Mavrodi et al., 2001; McSpadden-Gardener et al.,2000). Fluorescent pseudomonads that produce DAPG playa key role in the natural biological control of mostimportant crop diseases, such as tomato crown and root rot,wheat take-all, black root rot of tobacco or cucumber, sugardamping off, and tomato Fusarium wilt (Dwivedi and Johri,2003; Keel et al., 1996; KeU et al., 1992; Nowak-Thompsonet al., 1994). The growth medium and nutrients affect the levels ofantibiotics and population densities in biocontrol bacteria.In Pseudomonas spp., the antibiotic DAPG is produced athigh levels in the presence of glucose, gluconic acid, andzinc (Duffy and Defago, 1997; 1999; Werra et al., 2009).Although several potential biocontrol agents to controltomato Fusarium wilt have been isolated and characterized,no reports are available on effective biocontrol in the field.For development of biological control agents againsttomato Fusarium wilt, strain NJ134 was isolated fromrhizosphere and suppressive soils in Jeonnam province,South Korea (Lee, 2009). A rhizobacterium NJ134 showedmost effective inhibition against mycelial growth of thepathogen (KACC 40037). Based on 16S ribosomal DNAsequence analysis, the bacterial strain was identified asPseudomonas sp. (GenBank: FJ627993.1, National Centerfor Biotechnology Information (NCBI), U.S.A.). An anti-

plant pathology journal/the plant pathology journal

Mannitol Amendment as a Carbon Source in a Bean-based Formulation Enhances Biocontrol Efficacy of a 2,4-diacetylphloroglucinol-producing Pseudomonas sp. NJ134 Against Tomato Fusarium Wilt